Category Construction

Compared to walls and floors, it is usually relatively simple to add insulation to the ceiling of a building. Insulation thickness can generally be increased without adding structure or other complications. Gravity holds the insulation in place, and the only disadvantage is a loss of attic space. In addition, the ceiling is where most of the heat is gained or lost from an insulated space, so the addition of insulation is especially effective.

The only complication occurs at the edge of the building where roof structure typically restricts the potential for insulation thickness. In standard construc­tion, it is common to compress the insulation in this area and allow for ventilation using vent channels made especially for this purpose (see 201). But for superin­sulated buildings, the compression of insulation in this area is not acceptable.

To overcome the problem, several strategies have been developed:

Rigid insulation—Because rigid insulation can have R-values approximately double that of batt insulation, it may provide thermal protection at the edge of the ceiling without any adjustments to the framing (see 199A). This strategy may not be feasible when the roof pitch is very low, when rafter depth is shallow, or when the ceiling insulation value is very high.

Raised-heel truss—It is quite common when ordering trusses to specify a truss that has extra depth at the ends to accommodate extra insulation. This is called a raised-heel truss. Raised-heel trusses require blocking to prevent rotation, but otherwise are installed just the same as standard trusses (see 199B).

Dropped ceiling—Full insulation thickness at the edge of the building can also be accommodated by dropping the ceiling below the top plate. To maintain a given ceiling height, this strategy would require extra­length studs, extra siding, extra framing material for the ceiling, and extra labor. When using rafters (not trusses), a balloon-framed ceiling/wall connection (see 41A & B) would allow ceiling joists to act as ties and not be redundant (see 199C).

Raised plate—Raising the rafters to the top of the ceiling joists can increase the insulation thickness by the depth of the joists. The depth of the joists and raf­ters combined can be sufficient for superinsulation.

The extra cost of this strategy would include an extra rim joist, an extra plate, extra siding, and labor. The raf­ters need to be tied directly to the joists to counteract the thrust of the rafters (see 199D).

Vaulted ceilings—Vaulted ceilings do not restrict insulation thickness at the edge of the building because the insulation follows the pitch of the roof. The insula­tion value of vaulted roofs is limited only by the thick­ness of the roof itself (see 204A & B).

REDUCTION OF R-VALUE IN ВАТТ INSULATION DUE TO COMPRESSION

Snow guards, or snow clips, are metal protrusions that are integrated with the roofing to prevent snow from sliding off the roof. They are either clipped to the top edge of the roofing material (tiles and slate) or are nailed integral with it (shakes and shingles). Snow guards are used at the rate of 10 to 30 guards per square, depending on roof steepness.

SNOW GUARDS

Most heat is potentially lost or gained through the roof, so ceilings and roofs are generally more heavily insulated than floors or walls. Building codes in most climates require R-30 in roofs. The temperature dif­ference between the two sides of a roof or ceiling can cause condensation when warm, moist interior air hits cold surfaces in the roof assembly. It is therefore important to place a vapor barrier on the warm side of the insulation (see the drawing above right) and, in most cases, to ventilate the roof (see 200).

Ceiling insulation—Ceiling insulation consists typi­cally of either fiberglass batts placed between ceiling joists before the ceiling is applied or loose-fill insula­tion blown (or poured) into place in the completed attic space. The loose-fill type has the advantage of filling tightly around trusses and other interruptions of the attic space and of being able to fill to any depth. With either type, the vapor barrier should be located on the warm side of the insulation.

When trusses or shallow rafters restrict the depth of insulation at the edges of the ceiling, ventilation channels may be needed (see 201). Baffles may also be required to keep insulation from obstructing roof intake vents or from being blown out of place.

Roof insulation—Roof insulation may be fiberglass batts or rigid insulation. If the rafters are deep enough, batts are the most economical. When the rafters do not have adequate depth for batts, rigid insulation must be fit between the rafters. In both cases, a 1-in. air space must be provided above the insulation for ventilating the roof.

When the rafters are exposed to the living space below, the roof must be insulated from above. Rigid insulation is typically used because of its compactness and/or its structural value. Some roofing materials may be applied directly to the rigid insulation (e. g., mem­brane roofing on flat roofs); others require additional structure and/or an air space for ventilation.

Introduction

SHOE (SHOWN) AT PAVED SURFACES OR SPLASH OR PLASTiC GUARD CAP (NOT SHOWN)

AT CONNECTiON TO DRAiN PiPE

SPLASH BLOCK AT LOCATiONS WHERE DOWNSPOUT iS NOT CONNECTED TO DRAiN PiPE. BEFORE RELYiNG ON A SPLASH BLOCK, VERiFY LACK OF NEED TO CARRY WATER TO STORM SEWER OR DRY WELL.

PARTS OF A GUTTER SYSTEM

OGEE iS THE MOST COMMON GUTTER SHAPE. AVAiLABLE iN SiTE-FORMED ALUMiNUM Or GALVANiZED iN A VARiETY OF SizES, iT iS Also Made iN unpAINTED GALVANizED STEEL OR cOppER.

wOODEN GuTTERS ARE used extensively IN THE NORTHEAST. THEY ARE DiFFicuLT TO JOIN AT cORNERS OR FOR LONG LENGTHS & ARE pRONE

to decay.

concealed gutters OF

VARIABLE SHApES & SizES MAY BE DESIGNED TO FIT BEHIND THE FASciA OR wiTHiN THE SLOpE OF A ROOF. THESE ARE ALwAYS cuSTOM MADE & ARE THEREFORE ExpENSIVE. upper edge of gutter is typically lapped by

ROOFING; LOwER EDGE

caps fascia.

^ GUTTER SHAPES

SPECIAL GUTTERS

bracket hangers are

AVAiLABLE FOR ALL TYpES OF GuTTER; ScREw TO FASciA OR (wiTH LONGER ScREwS) TO RAFTER TAILS.

spike & ferrule HANGERS ARE used with BEVELED OR OGEE gutters; spike TO fascia OR

TO RAFTER TAILS. THE NEED FOR expansion joints IS GREATEST with this type of connector (maximum run without JOINT IS 40 FT.).

strap hangers are used with

METAL HALF-ROuND GuTTERS; NAIL OR ScREw TO ROOF SHEATHING OR THROuGH SHEATHING TO TOp OF RAFTER.

uncommon, archaic.

GUTTER HANGERS

NOTES

FASCIA IS SHOWN PLUMB FOR EASE OF INSTALLATION OF COMMON GUTTERS.

SQUARE-CUT RAFTER TAILS WORK WHERE THERE ARE NO GUTTERS OR WHERE HALF-ROUND GUTTERS ARE HUNG FROM STRAP HANGERS.

SEE 195C

FASCIA IS GENERALLY 2X MATERIAL FOR EASE OF INSTALLATION OF COMMON GUTTERS.

IN SOME AREAS. THE 2X IS USED AS A SUB-FASCIA AND COVERED WITH A HIGHER GRADE 1X FASCIA. GUTTERS MAY BE HUNG FROM A SINGLE – IX FASCIA. BUT SPIKES MUST BE LOCATED AT RAFTERS & FASCIA PREDRILLED TO PREVENT SPLITTING. BRACKETS SHOULD BE LOCATED NEAR RAFTERS.

Profiles

metal ridge

FLASHiNG MADE FRoM SAME MATERIAL AS

roofing

closure FLASHiNG at top of METAL roofing KEEPS out insects &

wiND-DRiVEN RAIN; FLASHiNG LAPS 30-LB. FELT uNDERLAYMENT.

BEAD of caulking or SEALANT AT TOP EDGE oF

lower roofing panel forms a dam against wind-driven rain.

top roofing panel nests AGAINST lower PANEL, forming tight seal.

SHEATHING

pitch-change FRAMING SEE 133B

METAL-ROOF PITCH CHANGE

GUTTER HANGER TYPES SEE 195C

connect down­spout TO DRAiN pipE or to splash block.

SEE 194

DOWNSpOUT FOR Every 40 FT. OF GUTTER

Clay tiles have been used in warm climates for centuries. Their use is still common in the southern extremes of this country, but they have recently been superseded by concrete tiles, which cost less and have better quality control.

Concrete tiles are made from high-density concrete coated with a waterproof resin. They are available in a variety of shapes and colors. Most tile patterns fall in the range of 16 in. to 18 in. long and 9 in. to 13 in. wide. Tiles weigh from 6 lb. to 10V2 lb. per square
foot (psf), which is about 21/2 to 5 times the weight of asphalt shingles. This extra weight may require that the roof structure be bolstered in some situations.

The cost of concrete tiles themselves is high com­pared to other common roofing materials, but most concrete tile-roof systems have a 50-year warranty.

Most manufacturers recommend installing the tiles on solid sheathing with 30-lb. felt underlayment and pressure-treated nailing battens under each course. Course spacing is usually about 13 in., and can be adjusted to make courses equal on each slope of roof.

CONCRETE-TILE ROOFING

Introduction & Types of Tile

30-LB. FELT

underlayment

OVER SOLiD SHEATHiNG; FELT LAPPED 21/2 iN. AT HORiZONTAL JOiNTS, 6 iN. AT JOiNTS PARALLEL TO SLOPE.

STAGGER JOiNTS BETWEEN TiLES ON ALTERNATE COuRSES.

дЛ CONCRETE-TILE ROOFING

CONCRETE-TILE VALLEY & HIP

@ CONCRETE-TILE EAVE

CONCRETE-TILE RAKE

Tile Rake

FLASHING WITH EDGE TURNED UP FORMS CHANNEL UNDER EDGE OF FIELD TILES & WITH DRIP AT BARGE

CONCRETE-TILE RAKE

Metal Rake

Low-cost metal roofs of aluminum or galvanized steel have been used for some time on agricultural and industrial buildings. The rolled metal panels are light­weight, long-lasting, and extremely simple to install. New panel patterns and new finishes have made metal roofing popular for residential and commercial build­ings. A baked-on or porcelain enamel finish is often warranteed for 20 years, and the galvanized steel or aluminum over which it is applied will last for another 20 years in most climates.

Rolled-metal sheets are typically 2 ft. to 3 ft. wide and are factory-cut to the full length of the roof from eave to ridge. Because of the difficulty of field cutting at angles, metal roofs are best suited to simple shed or gable roofs without extensive valleys and hips. Small openings such as vents should be kept to a minimum and collected wherever possible into single openings. (Vents are best located at the ridge, where they are most easily flashed with the ridge flashing.)

The width of the roof itself should be carefully coor­dinated with the width of roofing panels so that rake

trim, dormers, skylights, and other interruptions of the simple system will be located at an uncut factory edge.

Because the metal roofing has structural capacity, it is possible to install the roofing over purlins, which are 2x’s spaced 2 ft. to 4 ft. apart. Most metal roofing panels will span 4 ft. or more, so the load on each purlin is great, and the design of the purlins that support the roofing is a critical factor.

A wide range of finish colors is available with coor­dinated flashing and trim metal. Translucent fiberglass or plastic panels that match the profile of some metal roofing patterns are also available as skylights.

Choose fasteners and flashing that are compatible with the roofing in order to avoid corrosive galvanic action. Care must also be taken to avoid condensa­tion, which can occur on metal roofs. In cold climates, where proper ventilation of the roofing system does not suffice, a fiberboard backing covered with 30-lb. felt (installed parallel to the roofing panels) will insulate the roofing from moisture-laden air and also provide pro­tection from what little condensation does occur.

(g) PREFORMED METAL ROOFING

Ribbed Roofing

SCREW (OR NAiL) WiTH NEOPRENE WASHER LOCATED iN FLAT (VALLEY) PART OF ROOFiNG PROMOTES TiGHT SEAL OF wASHER.

Snap-Together Roofing

subsequent piEcE snap-fastens TO edge OF piEcE pREVIOuSLy NAILED. Flat-Head NAiL iS cOVERED SO neoprene washer is unnecessary. sections ARE NARROWER FOR this type.

Corrugated Roofing

screw (OR NAIL) WiTH NEOpRENE WASHER IS LOcATED ON RIDGE OF corrugation because VALLEYS ARE NOT WIDE OR FLAT ENOuGH.

IT’S difficult to adjust

TENSION OF NAiL OR ScREW.

WOOD-SHINGLE RIDGE

Wood shakes are popular for their rustic look and their durability. They are made from the same materials as wood shingles, but they are split to achieve a taper instead of being sawn. Shakes may have split faces and sawn backs or be taper-split with both sides having a split surface. In either case, the split side is exposed to the weather because it has small smooth grooves parallel to the grain that channel rainwater down the surface of the shake. Because the weather side of the shake is split, not sawn, and because they are consider­ably thicker, shakes will last a great deal longer than wood shingles made of the same material.

Standard shakes are 18 in. or 24 in. long and come in heavy or medium thickness. Wood shakes may be applied over open sheathing (see 166) or solid sheathing (see 163). The courses of shakes are usu­ally alternated with an interlayment of 30-lb. felt that retards the penetration of moisture through the relatively large gaps between shakes. Solid sheathing and cold-climate eave flashing (see 169B) are recom­mended in areas that have wind-driven snow.

30-LB. FELT INTERLAYMENT LAPS VALLEY FLASHiNG.

note

wood-shake ridge is similar to hip.

ASPHALT-SHINGLE RIDGE

For centuries, wood shingles have been used exten­sively for roofing, and they continue to be very pop­ular. However, with the advent of the asphalt shingle, they have recently lost their dominance as a roofing material. Furthermore, their use continues to decline because of cost increases and a drop in the quality of the raw materials.

Roof shingles are made predominantly from clear western red cedar, but are also available in redwood and cypress. They are sawn on both sides to a taper, and have a uniform butt thickness. Standard shingles are 16 in. long; 18-in. and 24-in. lengths are also avail­able. Widths are random, usually in the 3-in. to 10-in. range. There are several grades of wood shingles; only the highest grade should be used for roofing.

In most cases, wood shingles will last longer if applied over open sheathing (see 166) because they will be able to breathe and dry out from both sides and therefore be less susceptible to rot and other moisture – related damage. Use solid sheathing and underlayment, however, for low pitch (3-in-12 and 3l/2-in-12) and in areas of severe wind-driven snow.

Chemically treated fire-rated shingles are available. They must be installed over solid sheathing that is cov­ered with a plastic-coated steel foil.

FLAT ROOF EDGE AT WALL

Roll roofing is an inexpensive roofing for shallow – pitch roofs (1-in-12 to 4-in-12). The 36-in. wide by 36-ft. long rolls are made with a fiberglass or organic felt base that is impregnated with asphalt and covered on the surface with mineral granules similar to asphalt shingles. Several colors are available. Roll roofing weighs 55 lb. to 90 lb. per square (100 sq. ft.). The average life expectancy for roll roofing ranges from 10 to 15 years; fiberglass-base roofing is the longest lasting. Fiberglass-base rolls are also more resistant to fire. A disadvantage of all roll roofing is that it can bubble upward when hot because, unlike asphalt shin­gles, it cannot adjust to dimensional change.

Roll roofing must be applied over solid sheathing and does not require underlayment. It is easily nailed in place without using any specialized equipment.

There are two basic types of roll roofing, single cov­erage and double coverage.

Single coverage—Single-coverage roofing rolls are uniformly surfaced with mineral granules and are applied directly to the roof sheathing with only a 2-in.

to 4-in. lap, which is sealed with roofing adhesive. The rolls may be parallel to the eaves or to the rake. The roofing may be applied using the concealed-nail method (see 180B) or the exposed-nail method (not shown). A minimum pitch of 2-in-12 is required for the exposed – nail method. Single coverage is the least expensive and the least durable of the roll-roofing methods.

Double coverage—Double-coverage rolls are half surfaced with mineral granules and half smooth. The smooth part of the roll is called the selvage. The rolls are lapped over each other so that the surfaced por­tion of each roll laps over the smooth portion of the previous course. Each course of roofing is sealed to the previous course with either cold asphalt adhesive or hot asphalt. In this fashion, the roof is covered with a double layer of felt. The double layer of felt weighs 110 lb. to 140 lb. per square. Double-coverage roofing is more expensive than single-coverage roofing, but it makes a more durable roof. Double-coverage roll roofing may be applied with the courses parallel to the eave or to the rake (see 181A).

SINGLE-COVERAGE ROLL ROOFING

Conceded-Nail Method

дЛ DOUBLE-COVERAGE ROLL ROOFING

ROLL-ROOFING VALLEY & HIP (OR RIDGE)

Double or Single Coverage

Composite asphalt shingles are almost the perfect roofing material. They are inexpensive, waterproof, lightweight, and easily cut and bent. That is why asphalt shingles are so popular nationwide. They are available in a wide range of colors and textures, some with extra thickness to imitate shakes, slate, or other uneven materials. There is also a range of quality, with warran­ties from 15 to 30 years.

Asphalt shingles have a fiberglass or organic-felt base that is impregnated with asphalt and covered on the surface with granulated stone or ceramic material, which gives them color. Shingles made with fiberglass are more durable and more resistant to fire than those of organic felt.

Asphalt shingles must be applied over a solid sheathing covered with 15-lb. felt underlayment. They are easily nailed in place, using no specialized equip­ment. Many roofing contractors, however, use air – driven staples.

drip edge laps underlayment at rake.

rake flashing SEE 169c

THIRD course STARTS with full shingle minus one tab

FIRST course STARTS with full shingle

ASPHALT-SHINGLE ROOFING

EXTEND SHiNGLES 12 iN. (MiN

beyond centerline of valley.

Most skylights are manufactured with a complete flashing package and instructions for installation in a rough opening in the roof framing. Some are available with a kit to adapt the flashing to unusual roofing materials or pitches. Skylights are available in fixed or operable types with screens and/or sun-shade devices. Rough-opening sizes are specified and usually correspond with standard rafter spacing.

Many fixed skylights require a flashed curb to which the manufactured skylight is attached. With these sky­lights, the curb must be flashed like any other large penetration of the roofing surface, such as a dormer or a chimney (see 174 and 175C). Site-built curbless sky­lights are fixed and appear flush with the roof (see 176). Some codes prohibit these skylights because of the requirement for a curb.

For skylight framing, see 136A & B.

SKYLIGHT FLASHING

Notes

SKYLIGHT CURB FLASHING

For Use with Manufactured Skylight

A site-built curbless skylight is woven in with the roofing. Its bottom edge laps the roofing, and its top edge is lapped by roofing. This means that the skylight itself must be at a slightly lower pitch than the roof. Ledgers at the sides of the rough opening provide the support at this lower pitch. If built properly, there is no need for any caulking of these skylights except at the notch at the top of the side flashing. Insulated glass should limit condensation on the glazing, but any con­densation that does form can weep out through the clip notches in the bottom flashing. In extremely cold climates, the side flashing should be thermally isolated from the other flashing to prevent condensation on the flashing itself.

Curbless skylights are especially practical at the eave edge of a roof, where the lower edge of the skylight does not have to lap the roofing. This condition, often found in attached greenhouses, will simplify the details on this page because the slope of the skylight can be the same as the roof. The top and side details above right are suitable in such a case. Codes that require curbs preclude the use of these skylights.

@ CURBLESS SKYLIGHT

With the exception of wood roofs, which are now made with lower-grade material than in the past, today’s roofing materials will last longer than ever before, and can be installed with less labor. Composite materials now take the place of most natural roofing materials, including wood shingle and slate.

The selection of a roofing material must be care­fully coordinated with the design and construction of the roof itself. Some factors to consider are the type of roof sheathing (see 162-166), insulation (see 197-205), and flashing (see 167-176). For example, some roofing materials perform best on open sheathing, but others require solid sheathing. Some roofing materials may be applied over rigid insulation; others may not.

Many roofing materials require a waterproof under – layment to be installed over solid sheathing before roofing is applied. Underlayment, usually 15-lb. felt, which can be applied quickly, is often used to keep the building dry until the permanent roofing is applied.

In the case of wood shakes, the underlayment layer is woven in with the roofing courses and is called interlay – ment (see 186).

Other considerations for selecting a roofing material include cost, durability, fire resistance, local climatic conditions, and the slope (pitch) of the roof.

Cost—Considering both labor and materials, the least expensive roofing is roll roofing (see 180-181). Next in the order of expense are asphalt shingles (see 182-183), followed by preformed metal (see 190), wood shingles (see 184-185), shakes (see 186-187A), and tile (see 187B-189). Extremely expensive roofs such as slate and standing-seam metal are not discussed in depth in this book.

Durability—As would be expected, the materials that cost the most also last the longest. Concrete-tile roofs typically have a 50-year warranty. Shake and shingle roofs can last as long under proper conditions but are never put under warranty. Preformed metal and asphalt shingles are usually under a warranty in the 15-year to 30-year range.

Fire resistance—Tile and metal are the most resis­tant to fire, but fiberglass-based asphalt shingles and roll roofing can also be rated in the highest class for fire resistance. Wood shakes and shingles can be chemically treated to resist fire, but are not as resistant as other types of roofing.

Slope—The slope of a roof is measured as a propor­tion of rise to run of the roof. A 4-in-12 roof slope, for example, rises 4 in. for every 12 in. of run.

There are wide variations among roofing manu­facturers, but in general, the slope of a roof can be matched to the type of roofing. Flat roofs (У8-т-12 to!/4-in-12) are roofed with a built-up coating or with a single ply membrane (see 178-179). Shallow – slope roofs (1-in-12 to 4-in-12) are often roofed with roll roofing. Special measures may be taken to allow asphalt shingles on a 2-in-12 slope and wood shingles or shakes on a 3-in-12 slope, and some metal roofs may be applied to 1-in-12 slopes. Normal-slope roofs (4-in – 12 to 12-in-12) are the slopes required for most roofing materials. Some materials such as built-up roofing are designed for lower slopes and may not be applied to normal slopes.

Flat roofs aren’t actually flat, but must slope to drain water or manufacturers will not guarantee their products. The actual slope depends on the application, but most manufac­turers recommend 14 in. per ft. The slope may be achieved with the framing of the roof (see 139) or with tapered insula­tion. Water is usually contained at the edges of a flat roof with a curb or a wall and directed to a central drain (see 179B) or scupper at the edge of the roof (see 57D). A continuous gutter at the edge of a flat roof can also collect the water. The selection of an appropriate roofing system for a flat roof can be complicated. As with all roofs, climate is one factor. But the fact that a flat roof is covered with a large continuous waterproof membrane presents some special technical problems, such as expansion and contraction. If the roof is going to be used for a terrace or walkway, the effects of foot traffic must also be considered (see 56 and 57). For these reasons, a flat roof is best selected by a design profes­sional and constructed by a reputable roofing contractor. There are several application methods for flat roofs: Built-up roof—A built-up roof is composed of several layers of asphalt-impregnated felt interspersed with coats of hot tar (bitumen) and capped with gravel. This traditional and effective method is in widespread use. The applica­tion is technical and should be performed by professional roofers. Warranties range from one to five years.

WOODEN CURB WiTH CANT (SLOPE) TO PREVENT RiGHT ANGLES iN ROOFiNG MATERiAL METAL Flashing cONTiNuOuS OVER curb and with drip AT WALL SIDE

ROOFiNG Material cONTiNuOuS OVER TOp OF cuRB ROOF SHEATHING SHEATHING & WALL FINISH RAFTER

NOTE this curb is generally used in conjunction WiTH A scupper WHEN THE ROOF SLOpES TOWARD THE OuTSiDE EDGE OF THE BuiLDING. FOR ScuppER, SEE 57D.

PITCH-CHANGE FLASHING Posted by admin on 23/ 11/ 15 wall sheathing on framing of wood flue STEp FLASHiNG WOVEN WITH ROOFiNG COuRSES (shown before it is lapped with moisture barrier & SIDING), SEE 171C, OR ALTERNATIVE SIDEWALL FLASHiNG, SEE 171B. BASE FLASHiNG WRApS CORNERS, ExTENDS uNDER SHINGLES AT SIDES 4 IN. (MIN.) & LApS SHINGLES AT BASE 4 IN. (MIN.) OR ALTERNATIVE OuTSIDE CORNER FLASHiNG AT BOTH CORNERS, SEE 172A, COMBINED WITH ABuTTiNG ROOF FLASHiNG, SEE 169D. CHIMNEY FLASHING Wood-Framed Flue The flashing for a masonry chimney is best made of permanent materials such as copper or stainless steel. The flashing fits to the roof using the same principles as flashing for wood-framed flues (see 173B). The top edge of this flashing is then lapped with a counterflashing that is set into the mortar joints between masonry units. Because of the com­plex shapes, many of the pieces in chimney flashing cannot be folded but must be soldered or welded. A chimney located in the slope of the roof will require a cricket (also called a saddle), a ridged connection between chimney and roof that directs water away from the chimney. Most crickets may be formed with exterior-grade plywood; larger crickets may need to be framed like a typical roof. The entire surface of the cricket is flashed, as shown in the drawing below. SOLDERED CRICKET WRApS CORNERS, EXTENDS UNDER ROOFiNG 6 IN. (MiN.) AND TURNS Up AGAINST CHIMNEY 4 IN. (MIN.). In severe climates, a through-pan flashing that extends continuously through the chimney should be considered. Through-pan flashing prevents water from migrating through the masonry to a level below the flashing. It is made of lead or copper and is pen­etrated only by the flue. It is wrapped down at the edges, where it acts as counterflashing. The continuous flashing through the chimney does weaken the masonry bond, so this flashing should not be used in earthquake or hurricane zones. Modern roof jacks are typically fitted with neoprene gaskets sized to seal plumbing vents and other roof penetrations. Jacks are woven in with roofing mate­rials where possible. Jacks for metal roofs pose special problems. « Previous 1 2 3 4 … 7 Next » Tweet Copyright © 2025 Library builder - Articles about the repair, construction, interior design and landscaping, plumbing, electrical, waterproof wire, wire gas, building materials, construction machinery and equipment ...